Google has announced a new feature to enable people to follow trending topics happening in the world or even down to a specific country, as well as to receive notifications from Google on any specific topic they like, all of which are sent via email.
Simply go to Google Trends, and you'll see a subscribe button whenever you do a search for a topic. You then have the option to restrict it by country, and select how often you would like to be alerted to updates. However, these alerts aren't in real time; the most frequently you can be alerted is once per week.
For hottest topics, you can select how "hot" you would prefer to be alerted to: Hottest (only the hottest searches); Hotter (some hot searches); or Hot (all hot searches). These do have a higher frequency of alerts, however: as it happens, once a day, or once a week.
There is also a subscribe link on the left side where you can modify or cancel any alerts you're currently subscribed to.
The service is similar to the long-running Google Alerts service. However, Google Alerts has met with technical glitches, and Google ended their Alerts via RSS service last year, so there is speculation that Google Trends subscriptions could take the place of Google Alerts. However, the frequency of the Trends alerts being once a week on topics you search for will definitely make this service not as valuable as Google Alerts.